This invention relates to a method of prophylaxis and/or treatment of benign prostatic hyperplasia (BPH) in susceptible warm-blooded animals including man and in particular to a combination therapy involving administering a combination of drugs which inhibit sex steroid (androgens and estrogens) activity by blocking their formation and/or by blocking receptors where they act.
The role of androgens in the development of benign prostatic hyperplasia in men is well documented (Wilson, N. Engl. J. Med. 317: 628-629, 1987). In fact, benign prostatic hyperplasia does not develop in the absence of the testes (referred to in Wendel et al., J. Urol. 108: 116-119, 1972).
Blockade of testicular androgen secretion by surgical or medical (LHRH agonist) castration is known to decrease prostatic size (Auclair et al., Biochem. Biophys. Res. Commun. 76: 855-862, 1977; Auclair et al., Endocrinology 101: 1890-1893, 1977; Labrie et al., Int. J. Andrology, suppl. 2 (V. Hansson, ed.), Scriptor Publisher APR, pp. 303-318, 1978; Labrie et al., J. Andrology 1: 209-228, 1980; Tremblay and Belanger, Contraception 30: 483-497, 1984; Tremblay et al., Contraception 30: 585-598, 1984; Dube et al., Acta Endocrinol. (Copenh) 116: 413-417, 1987; Lacoste et al., Mol. Cell. Endocrinol. 56: 141-147, 1988; White, Ann. Surg. 22: 1-80, 1895; Faure et al., Fertil. Steril. 37: 416-424, 1982; Labrie et al., Endocrine Reviews 7: 67-74, 1986; Huggins and Stevens, J. Urol. 43: 705-714, 1940; Wendel et al., J. Urol. 108: 116-119, 1972; Peters and Walsh, N. Engl. J. Med. 317: 599-604, 1987; Gabrilove et al., J. Clin. Endocrinol. Metab. 64: 1331-1333, 1987).
Several studies have shown that treatment with an antiandrogen also decreases prostatic size (Neri et al., Endocrinology, 82: 311-317, 1968; Neri et al., Investigative Urology, 10: 123-130, 1972; Tunn et al., Acta Endocrinol. (Copenh.) 91: 373-384, 1979; Seguin et al., Mol. Cell. Endocrinol., 21: 37-41, 1981; Lefebvre et al., The Prostate 3: 569-578, 1982; Marchetti and Labrie, J. Steroid Biochem, 29: 691-698, 1988; Lacoste et al., Mol. Cell. Endocrinol. 56: 141-147, 1988; Tunn et al., Invest. Urol. 18: 289-292, 1980; Scott and Wade, J. Urol. 101: 81-85, 1969; Caine et al., J. Urol. 114: 564-568, 1975; Stone et al., J. Urol. 141: 240A, 1989; Clejan et al., J. Urol. 141: 534A, 1989).
U.S. Pat. No. 3,423,507 discloses the use of the antiandrogen cyproterone acetate (1.alpha.,2.beta.-methylene-6-chloro-17.alpha.-acetoxy-6-dehydroprogestero ne) for the treatment of benign prostatic hyperplasia. The above-mentioned U.S. Pat. No. 3,423,507 is disadvantageous since such compound (cyproterone acetate) has same androgenic activity (Poyet and Labrie, Mol. Cell. Endocrinol. 32: 283-288, 1985; Labrie et al., J. Steroid Biochem. 28: 379-384, 1987) and, consequently, only a partial inhibition of androgen action is expected. Pure antiandrogens (U.S. Pat. No. 4,329,364) used alone, on the other hand, cause an increase in testosterone secretion, which can result in a higher degree of aromatization into estrogens, a situation expected from current knowledge to have negative effects on prostatic hyperplasia (Jacobi et al., Endocrinology 102: 1748-1755, 1978).
Several studies have shown that treatment with the combination of chemical castration (LHRH agonist) and an antiandrogen cause greater inhibition of prostatic size than either treatment used alone (Seguin et al., Mol. Cell. Endocrinol. 21: 37-41, 1981; Lefebvre et al., The Prostate 3: 569-578, 1982; Marchetti and Labrie, J. Steroid Biochem. 29: 691-698, 1988.
In the prostate as well as in many other tissues, testosterone is irreversibly converted by 5.alpha.-reductase into the more potent androgen dihydrotestosterone (Bruchovsky and Wilson, J. Biol. Chem. 243: 2012-2021, 1968; Wilson, Handbook of Physiology 5 (section 7), pp. 491-508, 1975). Inhibitors of 5.alpha.-reductase have been found to inhibit prostatic growth (Brooks et al., Endocrinology 109: 830, 1981; Brooks et al., Proc. Soc. Exp. Biol. Med. 169: 67, 1982; Brooks et al., Prostate 3: 35, 1982; Wenderoth et al., Endocrinology 113,569-573, 1983; McConnell et al., J. Urol. 141: 239A, 1989); Stoner, E., Lecture on the role of 5.alpha.-reductase inhibitor in benign prostatic hypertropy, 84th AUA Annual Meeting, Dallas, May 8, 1989.
The inhibitory effect of the 5.alpha.-reductase inhibitor Merck L 652,931 on prostatic and seminal vesicle development in the prepubertal rat was described in Proc. 71st Annual Meeting of Endocr. Soc. abst. #1165, p. 314, 1989. The inhibitory effect of MK-906 on dihydrotestosterone formation in men has been described in men by Gormley et al., in Proc. 71st Annual Meeting of Endocr. Soc., abst. #1225, p. 329, 1989; Imperato-McGinley et al., in Proc. 71st Annual Meeting of Endocr. Soc., abst. #1639, p. 432, 1989; Geller and Franson, in Proc. 71st Annual Meeting of Endocr. Soc., abst. #1640, p. 432, 1989 and Tenover et al., in Proc. 71st Annual Meeting of Endocr. Soc., abst. #583, p. 169, 1989. The activity of the 5.alpha.-reductase inhibitors N,N-diethyl-4-methyl-3-oxo-4-aza-5.alpha.-androstane-17.beta.-carboxamide (4-MA) and 6-methylene-4-pregnene-3,20-dione (LY 207320) has been described by Toomey et al., Proc. 71st Annual Meeting of Endocr. Soc., abst. #1226, p. 329, 1989.
In addition to the well known effect of androgens on prostatic growth, there are many studies which show that estrogens play also a role in proliferation of the prostate (Walsh and Wilson, J. Clin. Invest. 57: 1093-1097, 1976; Robinette et al., Invest. Urol. 15: 425-432, 1978; Moore et al., J. Clin. Invest. 63: 351-257, 1979). Moreover, estrogens have been shown to enhance androgen-induced prostatic growth in the dog (Walsh and Wilson, J. Clin. Invest. 57: 1093-1097, 1976; Jacobi et al., Endocrinology 102: 1748-1755, 1978; Tunn et al., Urol. Int. 35: 125-140, 1980). A possible explanation of this enhancing effect of estrogen on androgen-induced prostate growth, is the observation that 17.beta.-estradiol has been shown to increase androgen binding in the dog prostate (Moore et al., J. Clin. Invest. 63: 351-357, 1979).
The antiestrogen Tamoxifen has been shown to improve steroid-induced benign prostatic hyperplasia in the dog (Funke et al., Acta Endocrinol. 100: 462-472, 1982). Administration of the antiestrogen Tamoxifen in association with the steroidal antiandrogen cyproterone acetate in patients suffering from benign prostatic hyperplasia showed beneficial effects on the symptoms of the disease (Di Silverio et al., in Ipertrofia Prostatica Benigna (F. Di Silverio, F. Neumann and M. Tannenbaum, eds), Excerpta Medica, pp. 117-125, 1986). In U.S. Pat. No. 4,310,523, it is proposed that a combination of an antiandrogen and an antiestrogen is effective for the prophylaxis and/or therapy of benign prostatic hyperplasia. Tamoxifen, however, has intrinsic estrogenic activity which limits its effectiveness.
Estrogen formation resulting from aromatization of androgens, occurs at several sites. In the male, aromatization of androgens has been demonstrated in the testis, adipose and muscle tissue, skin, liver, brain and prostate (Schweikert et al., J. Clin. Endocrinol. Metab. 40: 413-417, 1975; Folker and James, J. Steroid Biochem. 49: 687-690, 1983; Longcope et al., J. Clin. Endocrinol. Metab. 46: 146-152, 1978; Lacoste and Labrie, unpublished data; Stone et al., The Prostate 9: 311-318, 1986; Stone et al., Urol. Res. 15: 165-167, 1987). There is evidence for an increased production of estrogens in the prostatic tissue of benign prostatic hyperplasia patients (Stone et al., The Prostate 9: 311-318, 1986). Such data indicate that the local formation of estrogens may play a crucial role in stimulating prostatic growth in excess of the action predicted by circulating estrogens.
U.S. Pat No. 4,472,382 discloses treatment of BPH with an antiandrogen and certain peptides which act as LH-RH agonists.
U.S. Pat No. 4,596,797 discloses aromatase inhibitors as a method of prophylaxis and/or treatment of prostatic hyperplasia.
U.S. Pat. No. 4,760,053 describes a treatment of certain cancers which combines an LHRH agonist with an antiandrogen and/or an antiestrogen and/or at least one inhibitor of sex steroid biosynthesis.
U.S. Pat. No. 4,775,660 discloses a method of treating breast cancer with a combination therapy which may include surgical or chemical prevention of ovarian secretions and administering an antiandrogen and an antiestrogen.
U.S. Pat. No. 4,659,695 discloses a method of treatment of prostate cancer in susceptible male animals including humans whose testicular hormonal secretions are blocked by surgical or chemical means, e.g. by use of an LHRH agonist, which comprises administering an antiandrogen, e.g. flutamide, in association with at least one inhibitor of sex steroid biosynthesis, e.g. aminoglutethimide and/or ketoconazole.
BPH is caused by increased activity of both androgens and estrogens. Because of such a dual etiology of BPH, proposed hormonal therapies have been less than satisfactory and have all been unpredictable while, frequently, causing unacceptable side-effects. Moreover, the prior art treatment seldomly resulted in a decrease in prostatic volume above about 20 to 30% with inconsistent effects on the symptomatology (Scott and Wade, J. Urol. 101: 81-85, 1969; Caine et al., J. Urol. 114: 564-568, 1975; Peters and Walsh, New Engl. J. Med. 317: 599-604, 1987; Gabrilove et al., J. Clin. Endocrinol. Metab. 64: 1331-1333, 1987; Stone et al., J. Urol. 141: 240A, 1989; Clejan et al., J. Urol. 141: 534A, 1989; Stoner, E., Lecture on the role of 5.alpha.-reductase inhibitor in benign prostatic hypertrophy, 84th AUA Annual Meeting, Dallas, May 8, 1989.